Well servicing fluid

ABSTRACT

A well servicing fluid formulated with ingredients comprising a viscosifying polymer that is a crosslinked copolymer of an ethylenically unsaturated dicarboxylic anhydride and an alkyl vinyl ether, or the di-acid thereof; a pH adjuster capable of maintaining a pH of 5.5 or greater; and a solvent. Methods of treating a well formation with the wellbore servicing fluid and methods of making the wellbore servicing fluid.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority to U.S. patentapplication Ser. No. 12/833,799, filed Jul. 9, 2010, entitled “WellServicing Fluid,” which is herein incorporated by reference.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to a well servicing fluiduseful for treating hydrocarbon producing wells, such as oil and naturalgas wells.

BACKGROUND

Hydraulic fracturing is a common stimulation technique used to enhanceproduction of fluids from subterranean formations in, for example, oil,gas, coal bed methane, and geothermal wells. In a typical hydraulicfracturing treatment operation, a viscosified fracturing fluid is pumpedat high pressures and high rates into a wellbore penetrating asubterranean formation to initiate and propagate a hydraulic fracture inthe formation. Subsequent stages of viscosified fracturing fluidcontaining particulate matter known as proppant, e.g., graded sand,ceramic particles, bauxite, or resin coated sand, are then typicallypumped into the created fracture. The proppant becomes deposited intothe fractures, forming a permeable proppant pack. Once the treatment iscompleted, the fracture closes onto the proppant pack, which maintainsthe fracture and provides a fluid pathway for hydrocarbons and/or otherformation fluids to flow into the wellbore.

Water or hydrocarbons have been commonly used as base fluids forfracturing. While usually effective, water-based fluids can be harmfulto certain types of formations, and are not effective at removing excesswater from a well (removing “water blocks”).

It is preferable that a fracturing fluid be compatible with carbondioxide or other gases. As used herein, the fluid or the polymer thereinis “compatible” if it does not form a significant amount of precipitateupon contact with the gas. Addition of carbon dioxide to a fracturingfluid provides gas pressure to assist in returning fluids to thewellbore after treatment.

The use of alcohols as base fluids has been previously suggested.Advantages of alcohols over water-based fluids include low freezingpoints, low surface tensions, high water solubilities, high vaporpressures, and good compatibility with formations. Alcohols have severalpotential safety issues relating to their low flash points, high vapordensities, and invisibility of flame. These safety issues can beproperly addressed by skilled operators to minimize any associatedrisks.

Methanol foams have been prepared using synthetic polymers(polyacrylamide and polyethylene oxide). Attempts were made to crosslinkthe gelled methanol using metal crosslinking compounds. These includethe use of titanium crosslinked fluids marketed by service companies,such as, for example, METHOFRAC™ 3, available from BJ Services CompanyLLC, and METHOFRAC XL, also available from BJ Services Company LLC.These typically contain several percent of water, either for gellingand/or for breaking the gels. The titanium crosslinked polymers in thefluids do not break completely without the water and also do not performwell at temperatures greater than 90° C. Without water, this polymersystem is not compatible with carbon dioxide.

A modified guar polymer was reported to dissolve in anhydrous methanoland crosslinked with a borate complexor. The resulting complex wasbroken with an oxidizing breaker. This polymer as well as the boratecrosslinking compound are not compatible with carbon dioxide (i.e.formed a precipitate and the borate crosslink was reversed).

SPE 13565 (S. C. Crema and R. R. Alm, 1985; presented at theInternational Symposium on Oilfield and Geothermal Chemistry, Phoenix,Ariz., Apr. 9 11, 1985) describes the preparation of foamed anhydrousmethanol. The foamed material is offered for the stimulation of watersensitive formations. The foams contain a fluorosurfactant and a foamextender. The foam extender allows a reduction in the amount offluorosurfactant needed. Example foam extenders include oxyalkylatedfatty alcohols and amines or polyethers containing ethylene andpropylene oxide units. Foamed fluids have limited viscosity, and as aresult, their practical application is limited.

SPE 14656 (C. M. Fairless and W. Joseph, 1986; prepared for presentationat the East Texas Regional Meeting of the Society of PetroleumEngineers, Tyler, Tex., Apr. 21 22, 1986) describes the use of atwo-phase structured system for the treatment of wells. Vaporized carbondioxide is dispersed as an internal phase in a gelled complexed methanolexternal phase to produce a foam. The foams were used to treat watersensitive formations.

SPE 22800 (J. E. Thompson et al., July 1992) suggests a continuous mixprocess for gelling anhydrous methanol. The continuous mix process issuggested as a less risky alternative to batch processing. Additionally,the continuous process achieved full fluid viscosity in a reduced amountof time, and the performance of the produced materials was similar.

SPE 27007 (J. M Hernandez et al., 1994; prepared for presentation at theLatin American/Caribbean Petroleum Engineering Conference, Buenos Aires,Argentina, Apr. 27 29, 1994) presents a comparison of methanol and otherfluids as fracture fluids in gas wells. Methanol was shown to provideadditional stimulation near the fracture faces, decrease the saturationof water in the zone, and increased the gas permeability of theformation

SPE 35577 (D. B. Bennion, et al., 1996; prepared for presentation at theGas Technology Conference, Calgary, Alberta, Canada, Apr. 29 May 1,1996) offers a review of efforts taken to obtain natural gas in lowpermeability sandstone and carbonate formations. Methanol is suggestedas being able to significantly reduce interfacial tension betweenwater-gas or oil-gas systems.

SPE 70009 (Mark R. Malone, 2001; prepared for presentation at the SPEPermian Basin Oil and Gas Recovery Conference, Midland, Tex., May 15 16,2001) describes the use of crosslinked methanol fracturing fluids inwater-sensitive formations. A crosslinked methanol system was preparedusing hydroxypropyl guar, encapsulated ammonium persulfate breaker, andliquid carbon dioxide. Case histories were described using thefracturing fluids in test wells.

Another type of well servicing fluid is gravel packing fluid. Gravelpacking fluid has relatively large grained sand, e.g., gravel, suspendedtherein that may be utilized to prevent migration of smaller grainedsand from the subterranean formation into the well bore and to maintainthe integrity of the formation. In gravel packing operations, apermeable screen may be placed against the face of the subterraneanformation, followed by pumping the gravel packing fluid into the annulusof the well bore such that gravel becomes packed against the exterior ofthe screen.

Gravel packing fluids are often aqueous based fluids. The aqueous baseis known to include either freshwater, produced water or brines. Gravelpacking fluids generally include a viscosifier that can provideappropriate viscosity to allow effective suspension and/or transport ofthe gravel.

While advances have been made in well servicing fluids, furtherimprovements in well servicing fluids would be a welcome addition in thefield.

SUMMARY

The well servicing fluids of the present disclosure can provide one ormore of the following advantages: shear thinning properties suitable fortransporting proppant; high/low shear viscosity suitable fortransporting proppant; improved fluid loss control, reduced damage tothe formation, improved ability to maintain viscosity at elevatedtemperatures, and alcohol containing compositions that have improvedcompatibility with carbon dioxide.

An embodiment of the present disclosure is directed to a well servicingfluid. The well servicing fluid is formulated with ingredientscomprising a viscosifying polymer that is a crosslinked copolymer of anethylenically unsaturated dicarboxylic anhydride and an alkyl vinylether, or the di-acid thereof; a pH adjuster capable of maintaining a pHof 5.5 or greater; and a solvent.

Another embodiment of the present disclosure is directed to a method oftreating a well formation with a wellbore servicing fluid. The methodcomprises providing well servicing fluid formulated with ingredientscomprising: a viscosifying polymer that is a crosslinked copolymer of anethylenically unsaturated dicarboxylic anhydride and an alkyl vinylether, or the di-acid thereof; a pH adjuster capable of maintaining a pHof 5.5 or greater; and a solvent. The method further comprisesintroducing the well servicing fluid into a wellbore; and contacting theformation with the wellbore servicing fluid.

Yet another embodiment of the present disclosure is directed to a methodof making a well servicing fluid. The method comprises mixing aviscosifying polymer and a solvent at a first pH, the viscosifyingpolymer being a crosslinked copolymer of an ethylenically unsaturateddicarboxylic anhydride and an alkyl vinyl ether, or the di-acid thereof.A pH adjuster is mixed with the well servicing fluid to increase thefirst pH to a range of 5.5 or greater.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a table of OFITE® M900 viscosity data for differentconcentrations of STABILEZE® QM and methanol solutions at about 75° F.

FIG. 2 shows a graph of OFITE M900 viscosity data for differentconcentrations of STABILEZE QM in 75% methanol in water solutions at 75F.

FIG. 3 shows a graph of OFITE M900 viscosity data for differentconcentrations of STABILEZE QM in 80% methanol in water solutions at 75F.

FIG. 4 shows a graph of OFITE M900 viscosity data for differentconcentrations of STABILEZE QM in 90% methanol in water solutions at 75F.

FIG. 5 shows a graph of OFITE M900 Results Comparing viscosity ofMethanol/Water Solutions with 60 pptg STABILEZE QM.

FIG. 6 shows a graph of OFITE M900 Results Comparing viscosity ofMethanol/Water Solutions with 40 pptg STABILEZE QM.

FIG. 7 shows a graph of OFITE M900 Results Comparing Viscosity of allMethanol/Water Solutions with 40 and 60 pptg STABILEZE QM.

FIG. 8 shows a graph of OFITE M900 Results for Viscosity of all OFITETests Run with any Formulation of Methanol, Water, and STABILEZE QM.

FIG. 9 shows a table of Fann 50 viscosity Data for 80% Methanol in watersolution and 60 pptg STABILEZE QM @ 90° F.-150° F. and 100-25 sec⁻¹.

FIG. 10 shows a graph of Fann 50 viscosity Data for 80% Methanol inwater solution and 60 pptg STABILEZE QM @ 90° F.-150° F. and 100-25sec⁻¹.

FIG. 11 shows a table of Fann 50 viscosity Data for 90% Methanol inwater solution and 60 pptg STABILEZE QM @ 90-150° F. and 100-25 sec⁻¹.

FIG. 12 shows a graph of Fann 50 Viscosity Data for the 90% Methanol inwater solution and 60 pptg STABILEZE QM @ 90° F.-150° F. and 100-25sec⁻¹.

FIG. 13 shows a graph of Fann 50 Viscosity Data for the 80% Methanol and90% Methanol and 60 pptg STABILEZE QM @ 90° F.-150° F. and 100-25 sec⁻¹.

FIG. 14 shows a table of Fann 50 Viscosity Data for 80% Methanol inwater solution and 40 pptg STABILEZE QM @ 75° F.-250° F. and 100-25sec⁻¹.

FIG. 15 shows a graph of Fann 50 Viscosity Data for 80% Methanol and 40pptg STABILEZE QM @ 75° F.-250° F. and 100-25 sec⁻¹.

FIG. 16 shows a graph of Fann 50 Results for the 80% Methanol and 40pptg STABILEZE QM @ 75° F.-250° F. @ 100 sec⁻¹.

FIG. 17 shows a table of Fann 50 Viscosity Data for 80% Methanol inwater solution and 60 pptg STABILEZE QM @ 75° F.-250° F. and 100-25sec⁻¹.

FIG. 18 shows a graph of Fann 50 Results for the 80% Methanol in watersolution and 60 pptg STABILEZE QM @ 75° F.-250° F. @ 100-25 sec⁻¹.

FIG. 19 shows a graph of Fann 50 Results for the 80% Methanol in watersolution and 60 pptg STABILEZE QM @ 75° F.-250° F. @ 100 sec⁻¹.

FIG. 20 shows a graph of Fann 50 Results for the 80% Methanol Tests with60 pptg and 40 pptg STABILEZE QM @ 75° F.-250° F. @ 100 sec⁻¹.

FIG. 21 shows a table of Fann 50 Viscosity Data for 95% Methanol inwater solution and 60 pptg STABILEZE QM @ 75° F.-250° F. and 100-25sec⁻¹.

FIG. 22 shows a graph of Fann 50 Results for the 95% Methanol Tests with60 pptg STABILEZE QM @ 75° F.-250° F. @ 100-25 sec⁻¹.

FIG. 23 shows a table of OFITE M900 Viscosity Data for 80% Methanol inwater solution and 60 pptg STABILEZE QM @ 75° F.

FIG. 24 shows a graph of OFITE M900 Results for the 80% Methanol Testswith 60 pptg STABILEZE QM @ 75 @ 1.7-500 sec⁻¹ with the two differentMixing Methods.

FIG. 25 shows a graph of Fann 50 Results for 40% Methanol and 20-30 pptgSTABILEZE QM Tests @ 75° F.-250° F. at 100 sec⁻¹.

FIG. 26 shows a graph of Fann 50 Test Results for the 40% Methanol and18-20 pptg STABILEZE QM @ 150° F. and 100 sec⁻¹.

FIG. 27 shows a graph of Fann 50 Breaker Test Results for the 40%Methanol and 20 pptg STABILEZE QM and various loadings of GBW-5 breaker@ 150° F. and 100 sec⁻¹.

FIG. 28 shows a graph of Fann 50 Test Results for the 40% Methanol inwater solution and 20-23 pptg STABILEZE QM @ 250 F and 100 sec⁻¹.

FIG. 29 shows a graph of Fann 50 Breaker Test Results for the 40%Methanol, 22 pptg STABILEZE QM, and various loadings of GBW-5 breaker @225° F. and 100 sec⁻¹.

FIG. 30 shows a table of OFITE M900 Viscosity Data for 2% STABILEZE QMin 10.8 ppg Na/K Formate Brine at 75° F. and 107° F. @1.7-1020 sec⁻¹.

FIG. 31 shows a graph of OFITE M900 Results for 2% STABILEZE QM in 10.8ppg Na/K Formate Brine at 75° F. and 107° F.

FIG. 32 shows a table of OFITE M900 Viscosity Data for 2% STABILEZE QMwith 15.6 ppg Cesium Potassium Formate, Ambient Temperature and 107° F.@1.7-1020 sec⁻¹.

FIG. 33 shows a graph of OFITE M900 Results for 2% STABILEZE QM with15.6 ppg Cesium Potassium Formate, Ambient Temperature and 107° F.

FIG. 34 shows a table of OFITE M900 Results for 2% STABILEZE QM with18.5 ppg Cesium Formate at Ambient Temperature and 107° F. @1.7-1020sec⁻¹.

FIG. 35 shows a graph of OFITE M900 Results for 2% STABILEZE QM with18.5 ppg Cesium Formate at Ambient Temperature and 107° F.

FIG. 36 shows a table of OFITE M900 Results for 2% STABILEZE QM in 18.5ppg Cesium Formate at 140° F., 180° F.@1.7-1020 sec⁻¹.

FIG. 37 shows a graph of OFITE M900 Results for 2% STABILEZE QM in 18.5ppg Cesium Formate at 140° F., 180° F.

FIG. 38 shows a table of OFITE M900 Results for 3% STABILEZE QM with 12ppg Sodium Bromide Brine at pH=7 at 75° F., 107° F. and 140° F.@1.7-1020sec⁻¹.

FIG. 39 shows a graph of OFITE M900 Results for 3% STABILEZE QM with 12ppg Sodium Bromide at 75° F., 107° F. and 140° F. and at pH=7.0.

FIG. 40 shows a table of OFITE M900 Results for 3% STABILEZE QM with 12ppg Sodium Bromide Brine at pH=8 at 75° F., 107° F. and 140° F.@1.7-1020sec⁻¹.

FIG. 41 shows a graph of OFITE M900 Results for 3% STABILEZE QM in 12ppg Sodium Bromide at pH=8 at 75° F., 107° F. and 140° F.

FIG. 42 shows a table of OFITE M900 Results for 3% STABILEZE QM with 12ppg Sodium Bromide Brine at pH=10 at 75° F., 107° F. and 140°F.@1.7-1020 sec⁻¹

FIG. 43 shows a graph of OFITE M900 Results for 3% STABILEZE QM in 12ppg Sodium Bromide at pH=10 at 75° F., 107° F. and 140° F.

FIG. 44 shows a comparison between the rheology of 12 ppg Sodium bromideBrine viscosified with 3% STABILEZE QM at pH 7, 8 and 10 at 75° F., at75° F., 107° F. and 140° F. (pH adjusted using 50% NaOH).

FIG. 45 shows a graph of Caustic Treated STABILEZE QM Data.

FIG. 46 shows a graph of 1 pptg and 5 pptg STABILEZE QM in 40% MethanolFriction Data.

While the disclosure is susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and will be described in detail herein. However,it should be understood that the disclosure is not intended to belimited to the particular forms disclosed. Rather, the intention is tocover all modifications, equivalents and alternatives falling within thespirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

The present disclosure is directed to a well servicing fluid for use invarious applications, such as fracturing and gravel pack operations. Inan embodiment, the well servicing fluid can be formulated with aviscosifying polymer that is a crosslinked copolymer of an ethylenicallyunsaturated dicarboxylic anhydride and an alkyl vinyl ether; or thedi-acid thereof. In addition to the viscosifying polymer, the wellservicing fluids of the present disclosure can include a pH adjuster andat least one solvent chosen from alcohol and an aqueous solvent, such asfreshwater, produced water or brines, as discussed in greater detailbelow.

The Polymer

The viscosifying polymer can be a crosslinked copolymer of anethylenically unsaturated dicarboxylic anhydride and an alkyl vinylether; or the di-acid thereof.

Any suitable alkyl vinyl ether can be employed. For example, suitableethers include those with the general formal ROR′, where R is a C₁-C₄alkyl and R′ is vinyl group. In an embodiment, the ether is methyl vinylether.

Any suitable ethylenically unsaturated dicarboxylic anhydrides can beemployed. An example of a suitable anhydride is maleic anhydride.

Any suitable crosslinking compound can be employed. Examples of suitablecrosslinking compounds include diolefins, such as alpha, omega dieneshaving from 4 to 20 carbon atoms. In an embodiment, the crosslinkingcompound can be 1,9 decadiene.

Viscosifying polymers usable in the formulations of the presentdisclosure are well known in the art. One example of such a visocifyingpolymer is a poly (methyl vinyl ether/maleic anhydride) decadienecrosspolymer, which is available under the tradename STABILEZE QM, fromInternational Specialty Products of Wayne, N.J. A suitable example of adi-acid viscosifying polymer is poly (methyl vinyl ether/maleic acid)decadiene crosspolymer, which is available under the tradename STABILEZEXL-80W, from International Specialty Products of Wayne, N.J.

In an embodiment, the polymer can be formed by reacting an alkyl vinylether, maleic anhydride and a crosslinking compound. A suitable polymerinitiator may also be employed. A known method of making polymers thatcan be employed in the formulations according to an embodiment of thepresent disclosure is described in U.S. Pat. No. 5,874,510, issued Feb.23, 1999, to Yoon Tae Kwak, et al., the disclosure of which is herebyincorporated by reference in its entirety. The process is described formaking a crosslinked polymer of maleic anhydride and methyl vinyl etherin high yield. The process comprises precharging methyl vinyl ether,partially or totally, in isopropyl acetate and a crosslinker, into areactor maintained at about 60° to 80° C. Then continuous separatestreams of molten maleic anhydride and, if desired, the rest of methylvinyl ether, are fed into the reactor. The reaction mixture then ispolymerized at a temperature of about 60° to 80° C. A pumpable,homogeneous suspension of the desired crosslinked copolymer at a solidslevel of about 20-50 wt. % is formed. The reaction product is thenpumped from the reactor, the solvent is removed and the product isfiltered. A fine white powder of the crosslinked copolymer is obtained.In an embodiment, the crosslinker is 1,9-decadiene, which is present inan amount of at least 2.5 weight %; an initiator is employed, which canbe, for example, 2,2′-azobis(2-methylbutane-nitrile) or decanoylperoxide; an excess of methyl vinyl ether can be present during thepolymerization over the 1:1 mole ratio in the copolymer, the solidslevel of the resultant suspension is about 30-50%, and an excess ofmethyl vinyl ether is added continuously during the polymerization.

The viscosifying polymer can be employed to viscosify alcohol or aqueousbased mixtures, including fresh water, produced water, saturated brinesand unsaturated brines, such as heavy brines or seawater. When thepolymer is dispensed in the aqueous based mixtures, the acyl groups ofthe anhydride ring may hydrolyze to give free di-acid groups.

pH Adjuster

A pH adjuster can be used to raise the pH and gel the viscosifyingpolymer in order to provide a desired viscosity. Any suitable pHadjuster capable of achieving or maintaining a workable pH can beemployed. Suitable pH adjusters can include NaOH, KOH, Ca(OH)₂, sodiumbicarbonate, potassium carbonate, and sodium carbonate. The desired pHfor viscosifying the fluid can be 5.5 or greater, such as a pH rangingfrom about 7 to about 10 or 12.

Breakers

The breaker can generally be any breaker functional to degrade thepolymer under downhole conditions. In an embodiment, the breaker cangenerally be any oxidizing agent or encapsulated oxidizing agent. Forexample, the breaker can be a percarbonate, a perchlorate, a peracid, aperoxide, or a persulfate. The breaker can be encapsulated orunencapsulated. As an alternative to encapsulation, a low solubilitybreaker can be used. Specific examples of breakers include sodiumpersulfate and encapsulated potassium persulfate.

Solvent

The solvent can be any suitable organic or aqueous based solvent inwhich the polymer can dissolve. If the solvent is organic, it can beadvantageous for water to be soluble therein. Suitable organic solventsinclude alcohols, such as methanol, ethanol, 2-propanol (isopropylalcohol), 1-butanol and 2-butanol.

The solvent can be a mixture of both water and organic solvent. In suchmixtures, any amount of water can be employed. In an embodiment, thesolvent can comprise at least 20% by weight alcohol, based on the totalweight of the solvent. For example, the solvent can comprise 35% to 85%by weight alcohol, with the remaining solvent being an aqueous solvent,such as water, brine or produced water.

In an alternative embodiment, the solvent is substantially nonaqueous,where the term “substantially nonaquous” can mean that that solventincludes 5% by weight water or less, based on the total weight of thesolvent. Commercially available alcohol solvents often contain severalpercent of water (e.g., commercial methanol typically contains about 2percent water). If a well servicing fluid is to be used to remove waterform a down-hole formation, nonaqueous solvents with about 5% by weightwater or less, or about 2% by weight water or less, can be used.

In another embodiment, the solvent does not comprise substantial amountsof alcohol (e.g., is a substantially 100% aqueous based solvent). Anysuitable aqueous solvents can be employed. Examples of suitable aqueoussolvents include fresh water, brine, produced water, and combinationsthereof.

The brine may be any brine that serves as a suitable media for thevarious components. As a matter of convenience, in some cases the brinemay be the brine available at the site where the well servicing fluid isto be used. The brines may be prepared using salts, such as halide saltsand formates including, but not limited to, NaCl, KCl, CaCl₂, MgCl₂,NH₄Cl, CaBr₂, ZnBr₂, NaBr₂, sodium formate, potassium formate, cesiumformate and any other stimulation and completion brine salts. In anembodiment, the brine can be seawater. Brines based on halide salts andformates, in particular, can be difficult to viscosify. The ability ofthe disclosed viscosification polymers to viscosify such brines can bean advantage of the viscosifying polymers in an embodiment of thepresent disclosure.

The concentration of the salts in the brines can range from about 0.5%by weight of water up to saturation for a given salt. Exampleconcentrations of salts include 10%, 20%, 30% or more salt by weight ofwater. The brine may be a combination of one or more of the mentionedsalts, such as, for example, a brine prepared using NaCl and CaCl₂;NaCl, CaCl₂, NaBr and CaBr₂; sodium formate and potassium formate; orcesium formate and potassium formate.

In an embodiment, the aqueous based solvent can be a heavy brine. Heavybrines are defined as aqueous based solvents having a density greaterthan 9 ppg. Examples can include sodium chloride based brines having adensity of up to 10 ppg; calcium chloride brines having a density of upto 11.5 ppg; potassium chloride brines having a density up to 9.7 ppg;sodium formate brines having a density up to 10.9 ppg; NaCl/NaBr brineshaving a density up to 12.5 ppg; CaCl₂/CaBr₂ brines having a density upto 15.1 ppg; NaBr brines having a density up to 12.5 ppg; CaBr₂ brineshaving a density up to 15.3 ppg; Na/K formate brines having a density upto 13.1 ppg; Potassium formate brines having a density up to 13.1 ppg;CaBr₂/ZnBr₂ brines having a density up to 19.2 ppg; ZnBr₂ brines havinga density up to 21 ppg and cesium formate brines having a density up to19.3 ppg.

The total solvent can be a majority, by weight, of the well servicingfluid. The term majority is defined herein to mean 50% by weight ormore. In an embodiment, the solvent concentration can range from about75% to about 95% by weight based on the total weight of the wellservicing fluid.

Carbon Dioxide

The well servicing fluid can further comprise nitrogen (N₂) or carbondioxide (CO₂). The nitrogen or carbon dioxide can be present as a gas,as a liquid, or as a supercritical fluid. Typically, under hydraulicfracturing conditions, nitrogen is a gas and carbon dioxide existseither as a liquid or as a supercritical fluid.

Proppants

Proppants can be mixed with the well servicing fluids of the presentdisclosure. Any suitable proppant can be employed. Examples of suitableproppant includes graded sand, glass or ceramic beads or particles,sized calcium carbonate and other sized salts, bauxite grains, resincoated sand or particles, walnut shell fragments, aluminum pellets,nylon pellets, and combinations of the above.

Proppants are well known to be used in concentrations ranging from about0.05 to about 14 pounds per gallon (about 6 to about 1700 kg/m³) offracturing fluid composition, but higher or lower concentrations can beused as desired for the particular fracture design.

Other Ingredients

The well servicing fluid can comprise at least one additional compoundchosen from surfactants, non-emulsifiers, additional viscosifyingagents, clay stabilization additives, scale dissolvers, biopolymerdegradation additives, fluid loss control additives, high temperaturestabilizers, and other common and/or optional components.

Methods

The present disclosure is also directed to a method of servicing awellbore. The method comprises providing a well servicing fluid. Thewell servicing fluid is formulated with ingredients comprising: aviscosifying polymer that is a crosslinked copolymer of an ethylenicallyunsaturated dicarboxylic anhydride and an alkyl vinyl ether; or thedi-acid thereof. In addition to the viscosifying polymer, the wellservicing fluids of the present disclosure can include a pH adjuster andat least one solvent chosen from alcohol and an aqueous solvent. Themethod further comprises introducing the well servicing fluid into awell; and contacting the formation with the wellbore servicing fluid.

The providing step can involve obtaining the well servicing fluid in aprepared condition, or can involve obtaining the component ingredientsand preparing the well servicing fluid on site.

The well servicing fluid can further comprise any of the ingredientsdiscussed above, such as nitrogen, carbon dioxide, and proppant. Thesolvent can be any of the aqueous or organic solvents discussed above,or mixtures thereof. The pH adjuster can be any of those discussedabove. The breaker can be any of the breakers discussed above, includingpercarbonate, a perchlorate, a peracid, a peroxide, sodium persulfate,or encapsulated potassium persulfate.

The method can further comprise removing the well servicing fluid fromthe formation after the fluid contacts the formation. This removing stepcan be aided by gas pressure caused by the carbon dioxide or nitrogen.The contacting and removing steps can remove water from the formation.For effective removal of water from the formation, it is preferred thatthe well servicing fluid have reduced levels of water (if any water).The removed well servicing fluid can be recovered, recycled or disposedof according to industry standard practices.

The removing step can be performed at any time after the well servicingfluid contacts the formation. For example, the contacting step can beperformed for a sufficient time for removing water, followed by theremoving step. Alternatively, the well can be “shut in”, where thecontacting step is performed for a prolonged period of time. The lengthof time can be as short as immediate flow back or for up to several days(e.g. 2 or 3 days) shut in.

In an embodiment, the well servicing fluids of the present disclosureare introduced as a gravel pack fluid into a wellbore. Any suitablegravel packing technique can be employed. Various techniques for gravelpacking wells are generally well known in the art. In an embodiment, thewell bore servicing fluid comprising a crosslinked viscosifying polymer,a pH adjuster and a solvent, can further comprise gravel suspendedtherein. As part of the gravel packing process, a permeable screen maybe placed against the face of a subterranean formation, followed bypumping the well bore servicing fluid comprising the gravel into theannulus of the well bore such that gravel becomes packed against theformation on the exterior of the screen.

The well bore servicing fluids of the present application can also beemployed as fracturing or frac pack fluids. Any suitable fracturing orfrac packing technique can be employed. Various techniques forfracturing and frac packing wells are generally well known in the art.The well bore servicing fluid comprising a crosslinked viscosifyingpolymer, a pH adjuster and a solvent is pumped into the well bore at arate and a pressure sufficient to form fractures that extend into thesubterranean formation, providing additional pathways through whichfluids being produced can flow into the well bores. In an embodiment,the well bore servicing fluid can include a proppant. Well knownproppants used in fracturing and frac packing operations include, forexample, graded sand, bauxite, or resin coated sand. Any other suitableproppant can be suspended in the fracturing fluid. The proppant becomesdeposited into the fractures and thus holds the fractures open after thepressure exerted on the fracturing fluid has been released.

While the fluids are described herein as having use in fracturing fluidsand as gravel pack fluids, it is expected that the fluids of the presentdisclosure will find utility in completion fluids, fluid loss pills,lost circulation pills, diverter fluids, foamed fluids, stimulationfluids, and coiled tubing cleanout fluids used to clean the well bore,and the like.

The present disclosure is also directed to a method of making a wellservicing fluid. The method comprises mixing a viscosifying polymer anda solvent at a pH of less than 7, such as about 5.5 or less. Any of thevicosifying polymers and solvents disclosed herein can be used. Thesolvent can be an aqueous or organic based solvent, where theconcentration of the solvent is 50% by weight or more of the wellservicing fluid. The mixture can be heated to a suitable temperature fordissolving the viscosifying polymers in the solvent. Suitabletemperatures can be any temperature at which the viscosifying polymerwill dissolve, such as, for example, 150° F. or more. In an embodiment,the viscosifying polymers are mixed in a solvent comprising organicfluids, such as alcohol, without heating (e.g., mixing at roomtemperature) in order to dissolve the viscosifying polymer. After theviscosifying polymer has been solubilized to a desired degree in thesolvent, the pH of the mixture can be raised by adding a pH adjuster toprovide the desired viscosification of the fluid. For example, the pHcan be raised to a pH 5.5 or greater, such as a pH ranging from about 7to about 10 or 12.

The present disclosure will be further described with respect to thefollowing Examples, which are not meant to limit the invention, butrather to further illustrate the various embodiments.

EXAMPLES

Organic Solvent Formulations

Testing was carried out to determine if an example polymer of thepresent disclosure, having a tradename of STABILEZE QM, can be used toviscosify solutions containing up to 100% Methanol. The results aredescribed in the examples below. The example formulations employedmethanol as a solvent. The methanol fluid compositions can be used in,for example, unconventional reservoirs. The fluid also has otherapplications such as a coiled tubing cleanout fluid.

The STABILEZE QM polymer is manufactured by ISP and is used in, forexample, hair gel product applications. STABILEZE QM is a methyl vinylether-maleic anhydride copolymer crosslinked with 1,9-decadiene.

The STABILEZE QM was mixed in Methanol solutions. This involved addingthe STABILEZE QM to a Methanol-water mixture and neutralizing to a pH of7 with 25% sodium hydroxide. As the sodium hydroxide was added, thefluid gelled.

Test Procedures:

Initially, the fluid used for example solutions was prepared by heatingwater to 160° F. to dissolve the STABILEZE QM polymer. During the courseof the testing, an easier mixing procedure was found in which theSTABILEZE QM was added to a water/methanol mixture that did not requireheating the fluid. Both procedures are described below. Test data showedthat fluids prepared using both methods had similar rheologicalperformance.

Methanol solutions were made using the following formulations and theprocedures that follow:

Fluid Heated to 160° F.

For the example solutions prepared by heating, the grams needed toobtain the concentration of STABILEZE QM were added to tap water to forma 200 mL solution. The solution was mixed for 2 minutes using anoverhead Servodyne mixer at 1500 RPM. The STABILEZE QM dispersed in thewater created a white, cloudy solution. The water solution was thenplaced in a 160° F. water bath for 15 minutes. After 15 minutes, thesolution was mixed for 2 minutes (only slight cooling was allowed), andthe corresponding volume of Methanol was added. While mixing, thesolution was neutralized using 25% NaOH (about 0.20-0.25 mL) to pH 7.The solution began to gel.

Fluid with Caustic Addition

For example solutions prepared by mixing with caustic, the STABILEZE QMwas added to a Methanol-water mixture while stirring on an overheadstirrer without heating. While mixing, the solution was neutralizedusing the caustic (25% NaOH) to a pH 7. The solution began to gel.

When referring to “caustic” in the examples below, a 25% by weight NaOHsolution was employed.

OFITE M900 Procedure

For examples that were evaluated using the OFITE M900, as discussedbelow, base gel viscosity was measured on an OFITE M900 viscometer usinga R1B1 rotor-bob configuration with a closed cup. The viscosity wasmeasured at 1, 3, 6, 10, 30, 60, 100, 300 rpm and ramped down.

Fann 50 Procedure

In the Fann 50 testing discussed below, the fluid was initially shearedat 100 sec-1 followed by a shear rate sweep of 100, 80, 60, and 40 s⁻¹,at room temperature, to calculate power law indices n and K. The fluidwas sheared at 100 s⁻¹ in between shear rate sweeps, and the shear ratesweep was repeated as reported. A RIBS rotor-bob configuration was used.Test temperature ranges were 75° F.-150° F. and 75° F.-250° F.

OFITE M900 Tests for Methanol Fluids

Before running a series of Fann 50 tests on the different STABILEZE QMsolutions, the viscosity was measured using the OFITE M900 viscometer.The results for these OFITE M900 tests are shown in the table of FIG. 1and the charts of FIGS. 2-8.

Tests and Test Formulations

A. Fann 50 Tests were performed with Shear Ramps (100, 75, 50, 25) andTemp Ramps (90° F.-150° F. and 75° F.-250° F.) using the followingformulations:

A1. 80% Methanol 60 pptg STABILEZE QM @ (90° F.-150° F.) mixture. A2.90% Methanol 60 pptg STABILEZE QM @ (90° F.-150° F.) mixture.Temperature was increased 20 degrees every thirty minutes and a ShearRamp from about 100, 75, 50, 25 sec-1 for every temperature. Theseresults are shown in FIG. 11 and FIG. 12. FIG. 13 shows the FIG. 10 andFIG. 12 data combined.

B. Fann 50 Tests were also performed with Shear Ramps (about 100, 75,50, 25) and Temp Ramps (75° F.-250° F.) using the followingformulations:

B1. 80% Methanol 40 pptg STABILEZE QM @ (75° F.-250° F.) B2. 80%Methanol 60 pptg STABILEZE QM @ (75° F.-250° F.) B3. 95% Methanol 60pptg STABILEZE QM @ (75° F.-250° F.)Temperature was increased from about 75° F., to 110° F., to 150° F., to200° F., to 250° F. every thirty minutes and a Shear Ramp from about100, 75, 50, 25 sec-1 for every temperature. The results for formula B1are shown in FIG. 14, FIG. 15 and FIG. 16. The results for formula B2are shown in FIG. 17, FIG. 18 and FIG. 19. FIG. 20 shows the FIG. 16 andFIG. 19 data combined. The results for B3 are shown in FIG. 21 and FIG.22.

C. Fann 50 Tests were carried out with Shear Ramps (about 100, 75, 50,25 sec-1) and Temp Ramps (about 75° F.-250° F.) using the Caustic methodof fluid preparation. The formulations were made with 40% Methanol and20, 21, 23, and 30 pptg STABILEZE QM mixtures @ 75° F.-250° F. Theseresults are shown in FIG. 25.

D. Fann 50 Tests were carried out at 150° F. for formulations made with40% Methanol and 18 pptg and 20 pptg STABILEZE QM to form two separatemixtures. The mixtures were run for three hours @ 150° F. @ 100 sec-1.The results are shown in FIG. 26. Two additional formulations were madewith 40% Methanol and 20 pptg STABILEZE QM. To the first was added 0.5pptg of GBW-5 breaker (ammonium persulfate), and to the second was added2 pptg of GBW-5 breaker. These formulations were run for three hours @150° F. @ 100 sec-1. The results are shown in FIG. 27, along with theresults for the 20 pptg STABILIZE QM formulation without GBW-5 breaker.

E. Fann 50 Tests were run at 250° F. The formulations were made with 40%Methanol and 20, 21 and 23 pptg STABILEZE QM @ 250° F. and 100 sec-1.The results are shown in FIG. 28.

F. Fann 50 Tests were run at 225° F. Three formulations were made with40% Methanol and 22 pptg STABILEZE QM. To two of the formulations wasadded 2 and 3 pptg GBW-5 breaker @ 225° F. and 100 sec-1. These resultsare shown in FIG. 29, along with the results for the 22 pptg STABILIZEQM formulation without GBW-5 breaker.

G. Fann 50 Tests were run with Shear Ramps (about 100, 75, 50, 25) andTemp Ramps (about 75-250° F.). The formulations were prepared using theCaustic Method described above. Two formulations were made using 40%Methanol and 20 pptg and 30 pptg STABILEZE QM @ 100° F.-250° F.increasing the temperature 50 degrees every thirty minutes. Aformulation was also made using 40% Methanol and 40 pptg of caustictreated STABILEZE QM 40 from ISP. These results are shown in FIG. 45.

H. Friction Tests were also carried out. The friction tests employed amixture of 40% Methanol, 1 pptg and 5 pptg STABILEZE QM that wereprepared at 75° F. using the Caustic Method described above. Theseresults are shown in FIG. 46.

I. OFITE M900 Tests were performed on methanol fluids at 75° F. usingthe above described Caustic Method of fluid preparation. Theformulations were made of 80% methanol and 60 pptg STABILEZE QM. Theresults are shown in FIG. 23 and FIG. 24. These test results compare toFIG. 1 and FIG. 3 tests prepared using 160° F. water mixing procedure.FIG. 24 includes FIG. 3 data.

J. OFITE M900 Tests were performed on Na/K formate, Cs/K formate and Csformate containing fluids. The following formulations were made:

J1. 2% STABILEZE QM 10.8 ppg Na/K Formate at 75° F. and 107° F. J2. 2%STABILEZE QM 15.6 ppg Cs/K Formate at 75° F. and 107° F. J3. 2%STABILEZE QM 18.5 ppg Cs Formate at 75° F. and 107° F. J4. 2% STABILEZEQM 18.5 ppg Cs Formate at 140° F. and 180° F.The results for formulation J1 are shown in FIG. 30 and FIG. 31. Theseresults for formulation J2 are shown in FIG. 32 and FIG. 33. The resultsfor formulation J3 are shown in FIG. 34 and FIG. 35. The results forformulation J4 in FIG. 36 and FIG. 37.

K. CO₂ compatibility tests were carried out to determine thecompatibility of STABILEZE QM with CO₂. The formulation used forcompatibility testing was made with 60% Methanol, 40% water and 40 pptgSTABILEZE QM. The test device was a Large Chamber viewing cell used toinspect foams. This cell was oriented vertically. There were 2 valves onthe bottom of the viewing cell and 1 valve and a pressure regulator onthe top of the viewing cell. The following steps were taken for eachtest: 1) A 500 mL sample of the fluid was prepared at the prescribedconcentrations. 2) 300 mL of this fluid was poured into the viewing cellfrom the top through a funnel and the existing ½″ SS (stainless steel)tubing. This filled the chamber to about 50% of its volumetric capacity.3) The top valve and regulator were replaced. 4) CO₂ was then flowedfrom a dip (siphon) tube bottle with the flow being regulated by a CO₂pressure regulator. CO₂ was introduced into the bottom of the cell andeffectively bubbled up through the liquid fluid. The pressure on thechamber was controlled via the regulator on top of the viewing cell. 5)Observations were made looking for color changes, precipitates andsolids or any other indications that would be consistent with fluidincompatibility. 6) After all observations were completed, the pressurewas relieved via the top (a ventilator was used to evacuate the area ofany CO₂). The fluid was drained out and a 250 mL sample was captured ina glass graduated cylinder, which was placed on the counter top andobserved for 1 day. 7) The viewing cell was then cleaned and rinsed withsubstantial quantities of tap water.

Results

Results of Testing at about 75° F.—OFITE M900 Viscometer

A summary of the results of viscosity tests with 15 pptg, 20 pptg, 40pptg and 60 pptg STABILEZE QM in 75%, 80%, 90% and 95% Methanol inTomball tap water is shown in FIG. 1. As shown in FIG. 1, which showsviscosity data in centipoise, the viscosity of the mixtures decreaseswith increasing shear rate.

FIG. 2 shows the viscosity of 15 pptg, 20 pptg and 60 pptg STABILEZE QMin 75% Methanol at 75° F. in Tomball tap water. Results indicate thatthe viscosity of the fluid for 15 pptg, 20 pptg, and 60 pptg STABILEZEQM in 75% Methanol in Tomball tap water is 367 cP, 3185 cP and 6375 cPat 1.7 sec⁻¹, respectively. Results show that as the polymerconcentration was increased, the viscosity of the fluid increased.

FIG. 3 shows the viscosity of 40 pptg and 60 pptg STABILEZE QM in 80%Methanol at 75° F. in Tomball tap water. Results indicate that theviscosity of the fluid for 40 pptg and 60 pptg STABILEZE QM in 80%Methanol in Tomball tap water is 24500 cP and 30500 cP at 1.7 sec⁻¹,respectively. Results indicate that there was a slight increase as thepolymer loading was increased from 40 pptg to 60 pptg.

FIG. 4 shows the viscosity of 40 pptg and 60 pptg STABILEZE QM in 90%Methanol at 75° F. in Tomball tap water. Results indicate that theviscosity of the fluid for 40 pptg and 60 pptg STABILEZE QM in 90%Methanol in Tomball tap water is 5911 and 24900 cP at 1.7 sec⁻¹,respectively. These results indicate that the STABILEZE QM, at the 40pptg loading, loses significant viscosity when the Methanolconcentration is increased from 80% to 90% Methanol. However, theSTABILEZE QM, at the 60 pptg loading, loses a relatively small amount ofviscosity when the Methanol concentration is increased from 80% to 90%Methanol.

FIG. 5 shows the viscosity of 60 pt STABILEZE QM in 75%, 80%, 90% and95% Methanol at 75° F. in Tomball tap water. Results indicate that theviscosity of the fluid for 60 pptg STABILEZE QM in 75%, 80%, 90% and 95%Methanol in Tomball tap water is 6375, 30500, 24900 and 10300 cP at 1.7sec⁻¹, respectively. Results indicate that the viscosity increases asthe Methanol content increases from 75% to 80%, decreases slightly from80% to 90% and significantly decreases as the Methanol content increasesfrom 90% to 95%.

FIG. 6 shows the viscosity of 40 pptg STABILEZE QM in 80% and 90%Methanol at 75° F. in Tomball tap water. Results indicate that theviscosity of the fluid for 40 pptg STABILEZE QM in 80% and 90% Methanolin Tomball tap water is 24500 cP and 5911 cP at 1.7 sec⁻¹, respectively.These results again indicate that the STABILEZE QM, at 40 pptg loading,loses viscosity when the Methanol concentration is increased from 80% to90% Methanol. Results also show that the viscosity decrease, withdecrease in Methanol content, is significantly greater with lowerpolymer concentration—40 pptg vs. 60 pptg. Results also indicate thatthe addition of 1 gpt Clay Treat-3C to 40 pptg STABILEZE QM in 80%Methanol in Tomball tap water significantly reduces the viscosity of thefluid.

FIGS. 7 and 8 show a summary of all the fluids tested.

Results of Testing at about 90° F.-150° F.—Fann 50 Data

Results of viscosity tests at 90° F.-150° F. with 60 pptg STABILEZE QMin 80% Methanol in Tomball tap water are shown in FIG. 9 and FIG. 10.Results indicate that the fluid shows a slow reduction in viscosity withtemperature. The viscosity of the fluid at 90° F., 110° F., 130° F., and150° F. was 779, 713, 650 and 586 cP at 100 sec⁻¹, respectively.

Results of viscosity tests at 90° F.-150° F. with 60 pptg STABILEZE QMin 90% Methanol in Tomball tap water are shown in FIG. 11 and FIG. 12.Results indicate that the fluid shows a slow reduction in viscosity withtemperature. The viscosity of the fluid at 90° F., 110° F., 130° F., and150° F. was 820, 775, 656 and 559 cP at 100 sec⁻¹, respectively. Fann 50results from 90° F.-150° F. showed the 80% and 90% Methanol fluid with60 pptg STABILEZE QM had similar viscosity. FIG. 13 shows a summary ofdata shown in FIGS. 10 and 12.

Results of Testing at about 75° F.-250° F.—Fann 50 Data

Results of viscosity tests at 72° F.-250° F. with 40 pptg STABILEZE QMin 80% Methanol in Tomball tap water are shown in FIG. 14, FIG. 15 andFIG. 16. Results indicate that the fluid shows a reduction in viscositywith temperature. The viscosity of the fluid at 72° F., 110° F., 150°F., 200° F., and 250° F. was 1119, 958, 753, 515 and 305 cP at about 100sec⁻¹, respectively.

Results of viscosity tests at 72° F.-250° F. with 60 pptg STABILEZE QMin 80% Methanol in Tomball tap water are shown in FIG. 17, FIG. 18 andFIG. 19. Results indicate that the fluid shows a reduction in viscositywith temperature. The viscosity of the fluid at 72° F., 110° F., 150°F., 200° F., and 250° F. was 2055, 1598, 1372, 988 and 455 cP at 100sec⁻¹, respectively.

FIG. 20 shows a summary of data from FIG. 16 and FIG. 19.

Results of viscosity tests at 72° F.-250° F. with 60 pptg STABILEZE QMin 95% Methanol in Tomball tap water are in FIG. 21 and FIG. 22. Resultsindicate that the fluid shows much less viscosity than the 80% Methanolfluid and a significant reduction in viscosity with temperature. Theviscosity of the fluid at 72° F., 110° F., 150° F., 200° F., and 250° F.is 402, 280, 159, 67 and 33 cP at 100 sec⁻¹, respectively. Results alsoindicate that the viscosity of the fluid decreases significantly whenthe Methanol content is increased from 80% to 95%.

Results of OFITE M900 Testing at about 75° F. —Compare Heated to 160° F.Procedure and Caustic Addition Mixing Procedure

During the course of the testing, it was determined that the STABILEZEQM solutions could be more easily mixed by mixing STABILEZE QM in theMethanol water solution and adding caustic (NaOH) to the fluid to gel.Testing shown in FIG. 23 and FIG. 24 shows the comparison of theviscosity of a 60 pptg STABILEZE QM in 80% Methanol solution preparedusing both mixing procedures. Results indicate that the fluid preparedwithout heating showed higher viscosity at about 75° F.

Results of Testing at about 75° F.-250° F.—Fann 50 Data

Results of Fann 50 tests with 20, 21, 23 and 30 pptg STABILEZE QM in 40%Methanol are shown in FIG. 25. Results indicate that the viscosity at150° F. for 20, 21, 23, and 30 pptg STABILEZE QM in 40% Methanol was103, 256, 408 and 917 cP at 100 sec⁻¹, respectively. Results indicatethat the viscosity at 250° F. with 20, 21, 23 and 30 pptg STABILEZE QMin 40% Methanol was 71, 227, 208 and 587 cP at 100 sec⁻¹, respectively.

Results of Fann 50 tests with 18 and 20 pptg STABILEZE QM in 40%Methanol at 150° F. show that the fluids had 137 and 232 cP at 100sec⁻¹, respectively, after three hours at 150° F. Results are shown inFIG. 26. It is noted that 20 pptg data in FIG. 25 is higher than FIG. 24data. This could be due to a slight concentration difference ortemperature heat rate difference. Based on viscosity data at otherpolymer concentrations, the correct viscosity is probably 232 cP at 100sec⁻¹.

Results of Fann 50 breaker tests with 20 pptg STABILEZE QM in 40%Methanol with 0, 0.5 and 2 pptg GBW-5 show that the fluids had 232, 175and 51 cP at 100 sec⁻¹, respectively, after three hours at 150° F.Results indicate that the breaker reduced the viscosity of the fluid asthe fluid was heating to temperature, but showed very minimal viscosityreduction for the remainder of the test. Results are shown in FIG. 27.

Results of Fann 50 tests with 20, 21 and 23 pptg STABILEZE QM in 40%Methanol show that the fluids had 68, 68 and 126 cP at 100 sec′,respectively, after three hours at 250° F. Results are shown in FIG. 28.

Results of Fann 50 breaker tests with 22 pptg STABILEZE QM in 40%Methanol with 0, 2 and 3 pptg GBW-5 show that the fluids had 230, 103and 44 cP at 100 sec⁻¹, respectively, after three hours at 225° F.Results again indicate that the breaker reduced the viscosity of thefluid as the fluid was heating to temperature, but showed very minimalviscosity reduction for the remainder of the test. Results are shown inFIG. 29.

Results of Testing at about 75° F.-180° F. —OFITE M900 Data—FormateBased Fluids

Results of 2% STABILEZE QM testing in sodium/potassium formate,cesium/potassium formate and cesium formate fluids are shown in FIGS.30-37.

Results of testing in 10.8 ppg sodium/potassium formate indicate that,when completely mixed, the 2% STABILEZE QM in 10.8 ppg Na/K brine hascomparable viscosity at 75° F. and at 107° F. The fluids haveapproximately 100-110 cP at 100 sec⁻¹. The STABILEZE QM continues tosolubilize with time and temperature.

Results of testing in 15.6 ppg cesium/potassium formate indicate that,when completely mixed, the 2% STABILEZE QM in 15.6 ppg Cs/K brine hascomparable viscosity at 75° F. and at 107° F. The fluids haveapproximately 65 cP at 100 sec⁻¹. The viscosity of the 2% STABILEZE QMin 15.6 ppg Cs/K brine increases with temperature. The viscosity of the2% STABILEZE QM in 18.5 ppg Cesium Formate brine at 75° F., 107° F.,140° F. and 180° F. is 89, 98, 183, and 387 cP at 100 sec⁻¹,respectively. The viscosity of the 2% STABILEZE QM in 18.5 ppg in CesiumFormate brine at 75° F., 107° F., 140° F. and 180° F. is 309, 250,greater than 875, and 5605 cP at 1.7 sec⁻¹, respectively.

The two pre-neutralized STABILIZE QM powder products (caustic treatedSTABILIZE and caustic and quat treated STABILIZE 11638-61) from ISP weretested. Neither product gelled in 40% or 80% Methanol. The caustictreated STABILIZE in a 40% Methanol solution was very chunky, and mostof the powder did not dissolve, instead it clumped up. The fluid was runon the Fann 50, and data is shown in FIG. 45 below. The caustic treatedSTABILIZE QM did form a thick gel, when mixed in water, but not all thepowder completely dissolved.

CO₂ Compatibility Test Results

Results of CO₂ compatibility testing of 60% Methanol, 40% water and 40pptg STABILEZE QM showed that the fluid appeared to be compatible withCO₂. The test procedure is detailed above.

Friction Pressure Test Results

Results of friction pressure testing of 1 pptg and 5 pptg STABILEZE QMin 40% Methanol and 60% water, shown in FIG. 46, indicated that 1 pptgSTABILEZE QM in 40% Methanol shows no friction reduction. Increasing theSTABILEZE QM concentration to 5 pptg actually shows a friction pressureincrease.

Conclusions:

The STABILEZE QM was mixed in Methanol solutions by adding the STABILEZEQM to the Methanol-water mixture and neutralizing to pH 7 with 25%sodium hydroxide. As the sodium hydroxide was added, the fluid gelled.

Results indicate that as the polymer concentration increases from 15 to60 pptg the viscosity of the fluid increased.

The fluid viscosity for 15 pptg, 20 pptg, and 60 pptg STABILEZE QM in75% Methanol in Tomball tap water was 367, 3185 and 6375 cP at 1.7sec-1, respectively. Results indicate that as the polymer concentrationincreases the viscosity of the fluid increases.

The fluid viscosity for 40 pptg and 60 pptg STABILEZE QM in 80% Methanolin Tomball tap water is 24500 and 30500 cP at 1.7 sec-1, respectively.STABILEZE QM, at the 40 pptg loading, loses significant viscosity whenthe Methanol concentration is increased from 80% to 90% Methanol. TheSTABILEZE QM, at the 60 pptg loading, loses only minimal viscosity whenthe Methanol concentration is increased from 80% to 90% Methanol.

The viscosity of the 60 pptg STABILEZE QM in 75%, 80%, 90% and 95%Methanol in Tomball tap water is 6375, 30500, 24900 and 10300 cP at 1.7sec-1, respectively. The viscosity increases as the Methanol contentincreases from 75% to 80%, decreases slightly from 80% to 90% andsignificantly decreases as the Methanol content increases from 90% to95%.

The addition of Clay Treat-3C does significantly reduce the viscosity ofSTABILEZE QM Methanol fluids.

Fann 50 results from 90° F.-150° F. show the 80% and 90% Methanol fluidwith 60 pptg STABILEZE QM has similar viscosity. The viscosity of the80% Methanol fluid with 60 pptg STABILEZE QM at 90° F.-150° F. decreasesfrom 780 to 586 cP at 100 sec⁻¹.

The viscosity of the 80% Methanol fluid with 60 pptg STABILEZE QM at 72°F.-250° F. decreases from 2055 to 455 cP at 100 sec⁻¹. The viscositysignificantly decreases as the Methanol content increases from 80% to95% (note that no 90% tests were done). The viscosity of the 60 pptgSTABILEZE QM in 95% Methanol fluid at 72° F.-250° F. decreases from 402to 33 cP at 100 sec⁻¹.

Breaker tests with 18 and 20 pptg STABILEZE QM in 40% Methanol with 0,0.5 and 2 pptg GBW-5 breaker show that the fluids had 232, 175 and 51 cPat 100 sec-1, respectively, after three hours at 150° F. Resultsindicate that the breaker reduced the viscosity of the fluid as thefluid was heating to temperature, but showed very minimal viscosityreduction for the remainder of the test.

Breaker tests with 20, 21 and 23 pptg STABILEZE QM in 40% Methanol showthat the fluids had 68, 68 and 126 cP at 100 sec′, respectively, afterthree hours at 250° F.

Breaker tests with 22 pptg STABILEZE QM in 40% Methanol with 0, 2 and 3pptg GBW-5 at 225° F. show that the fluids had 230, 103 and 44 cP at 100sec′, respectively, after three hours at 225° F. Again the breakerreduced the viscosity of the fluid as the fluid was heating totemperature, but showed very minimal viscosity reduction for theremainder of the test.

Aqueous Solvent Formulations

The following examples illustrate that STABILEZE QM from ISP can geloilfield brines and maintain viscosity with time at temperature forpossible use as gravel pack fluids.

Procedure

Fluid Viscosity Determination at about 75° F.

10.8 ppg Na/K Formate was measured into a beaker. While stirring usingan overhead stirrer, the STABILEZE QM polymer was added and stirred for10 minutes. 40 milliliters of the gelled solution was added into aclosed viscometer cup. The viscosity was measured at 1, 3, 6, 10, 30,60, 100, 300 and 600 rpm on an OFITE M900 Viscometer with R1/B1rotor-bob configuration. This testing procedure was also used to testmixtures of 15.6 ppg Cesium/Potassium Formate and 18.5 Cesium Formateviscosified with the STABILEZE QM polymer.

Viscosification of 12 ppg Sodium Bromide was also carried out withSTABILEZE QM. 12 ppg Sodium Bromide Brine was measured into a beaker.While stirring using an overhead stirrer, STABILEZE QM was added andstirred for 15 minutes. 50% NaOH was used to adjust the pH. 150 ml ofthe gel was transferred into an open cup and fluid viscosity wasmeasured at ambient temperature at 1, 3, 6, 10, 20, 30, 60, 100, 300 and600 rpm on OFITE M900 Viscometer with R1/B1 rotor bob configuration.

The viscosity testing was performed for 2% STABILEZE QM in 10.8 ppg Na/Kformate, 15.6 ppg Cesium/Potassium Formate and 18.5 ppg Cesium Formateand 3% STABILEZE QM in 12 ppg Sodium bromide. The viscosity testsperformed with 3% STABILEZE QM in 12 ppg Sodium Bromide were buffered toa pH of 7, 8 and 10. The fluid formulations for these tests are given inthe Formulation Section below.

Stability Testing

The stability of 2% STABILEZE QM in 10.8 ppg Na/K Formate and 15.6 Cs/KFormate was tested as follows: After measuring the rheology at ambienttemperature, the gel was transferred into a glass jar and heated in apre-heated water bath for an hour at 107° F. The heating cup of theOFITE M900 Viscometer was then pre-heated to 107° F. The gel wastransferred into the heating cup at 107° F. and viscosity measured at 1,3, 6, 10, 20, 30, 60, 100, 300 and 600 rpm. The gel was cooled to roomtemperature and after an hour viscosity measurements were repeated.

The stability of 2% STABILEZE QM in 18.5 ppg Cs Formate was tested asfollows: The gel was transferred into a glass jar and heated in apre-heated water bath at 107° F. The heating cup of the OFITE M900Viscometer was then pre-heated to 107° F. In 1 hour the gel wastransferred into the heating cup at 107° F. and viscosity measured at 1,3, 6, 10, 20, 30, 60, 100, 300 and 600 rpm. The gel was poured back intothe glass jar and heated in a pre-heated water bath at 140° F. for anhour. The viscosity was measured again while the gel was kept in thepre-heated cup at 140° F. Now the gel was poured back into the glass jarand warmed in a pre-heated water bath at 180° F. for an hour. Theviscosity was measured again while the gel was heated using thepre-heated cup at 180° F. The gel was cooled to room temperature andafter an hour viscosity measurements were repeated.

The stability of 3% STABILEZE QM in 12 ppg Sodium Bromide was tested asfollows: The gel was transferred into a glass jar and heated in apre-heated water bath at 107° F. for an hour and rheology measured onOFITE M900 viscometer while keeping the gel heated in the pre-heated cupat 107° F. The gel was then transferred back into the glass jar and keptanother 20 hours in water bath maintained at 107° F. Rheologymeasurements were repeated as before using pre-heated cup at 107° F.after 20 hours. The gel was poured back into the glass jar and heated to140° F. in a pre-heated water bath for an hour. Rheology was measured at1, 3, 6, 10, 20, 30, 60, 100, 300 and 600 rpm.

Fluid Formulations:

Formulation No: 1

-   -   147 ml of 10.8 ppg Sodium/Potassium Formate Brine solution    -   3 gm STABILEZE QM    -   Viscosity testing performed at 75° F. and Stability testing        performed at 107° F. (see Procedure above)

Formulation No: 2

-   -   147 ml of 15.6 ppg Cesium/Potassium Formate Brine Solution    -   3 gm STABILEZE QM    -   Viscosity testing performed at 75° F. and Stability testing        performed at 107° F. (See Procedure above)

Formulation No: 3

-   -   147 ml of 18.5 ppg Cesium Formate Brine Solution    -   3 gm STABILEZE QM    -   Viscosity testing performed at 75° F. and Stability testing        performed at 107° F., 140° F. and 180° F.

Formulation No: 4

-   -   194 ml of 12 ppg Sodium Bromide Brine Solution    -   6 gm STABILEZE QM    -   pH 7 using 50% by weight NaOH    -   Viscosity testing performed at 75° F. and Stability testing        performed at 107° F. (1 hour), 107° F. (20 hours) and 140° F.

Formulation No: 5

-   -   194 ml of 12 ppg Sodium Bromide Brine Solution    -   6 gm STABILEZE QM    -   pH of 8 using 50% by weight NaOH    -   Viscosity testing performed at 75° F., and stability testing        performed at 107° F. (1 hour), 107° F. (20 hours) and 140° F.

Formulation No: 6

-   -   194 ml of 12 ppg Sodium Bromide Brine Solution    -   6 gm of STABILEZE QM    -   pH of 10 using 50% by weight NaOH    -   Viscosity testing performed at 75° F., and stability testing        performed at 107° F. (1 hour), 107° F. (20 hours) and 140° F.

Results:

Results of 2% STABILEZE QM in 10.8 Ppg Na/K Formate at about 75° F.,107° F.

The results of the viscosity testing of 2% STABILEZE QM in 10.8 ppgsodium/potassium formate at 75° F. and 107° F. are shown in FIG. 30 andFIG. 31. Results indicate that when completely mixed, the 2% STABILEZEQM in 10.8 ppg Na/K brine has comparable viscosity at 75° F. and at 107°F. The fluids have approximately 100-110 cP at 100 sec-1. The STABILEZEQM continues to solubilize with time and temperature.

Results of 2% STABILEZE QM in 15.6 Ppg Cesium/Potassium Formate

The viscosity of 2% STABILEZE QM in 15.6 ppg Cesium/Potassium Formate at75° F. and 107° F. is shown in FIG. 32 and FIG. 33. Results indicatethat when completely mixed, the 2% STABILEZE QM in 15.6 ppgcesium/potassium brine has comparable viscosity at 75° F. and at 107° F.The STABILEZE QM continues to solubilize with time and temperature.

Results of 2% STABILEZE QM in 18.5 Ppg Cesium Formate at about 75° F.,107° F., 140° F. And 180° F.

Rheology of 2% STABILEZE in 18.5 ppg Cesium formate at ambienttemperature and 107° F. are shown in FIG. 34 and FIG. 35. Resultsindicate that, when completely mixed, the 2% STABILEZE QM in 18.5 ppg Csformate brine has comparable viscosity at 75° F. and at 107° F. Thefluids have approximately 90 cP at 100 sec⁻¹. The viscosity of the 2%STABILEZE QM in 18.5 ppg Cs formate brine increases with temperature.The viscosity of the 2% STABILEZE QM in 18.5 ppg Cs formate brine at 75°F., 107° F., 140° F. and 180° F. is 89, 98, 183, and 387 cP at 100sec⁻¹, respectively. The viscosity of the 2% STABILEZE QM in 18.5 ppg Csformate brine at 75° F., 107° F., 140° F. and 180° F. is 309, 250,greater than 875, and 5605 cP at 1.7 sec⁻¹, respectively. FIG. 36 andFIG. 37 show the rheology of 2% STABILEZE QM in 18.5 ppg Cs Formate at140° F. and 180° F.

Results of 3% STABILEZE QM in 12 Ppg Sodium Bromide Brine at about 75°F., 107° F. And 140° F.

The viscosity of 3% STABILEZE QM in 12 ppg Sodium Bromide Brine bufferedto pH 7, 8 and 10 is shown in the tables of FIGS. 38, 40 and 42 and thedata is plotted in FIGS. 39, 41, and 43. Results indicate that 3%STABILEZE QM in 12 ppg Sodium bromide buffered to 7 pH, the viscosityincreased with temperature and time. The viscosity of the fluid at 75°F., 107° F. and 140° F. is respectively 627, 409, and 471 cP at 100sec-1.

Rheology testing of 12 ppg Sodium Bromide Brine viscosified with 3%STABILEZE buffered to pH 8 indicates comparable viscosities at lowershear rates. The viscosity of 12 ppg sodium bromide with 3% STABILEZE QMbuffered to pH 8 at 75° F., 107° F. and 140° F. is 495, 380, and 325 cPrespectively at about 100 sec-1.

Viscosity of 3% STABILEZE QM in 12 ppg Sodium Bromide buffered to 10 pHat 75° F., 107° F. and 140° F. is 555, 365, and 287 cP respectively atabout 100 sec-1. At higher temperatures, 12 ppg Sodium Bromide Brineviscosified with 3% STABILEZE QM at 10 pH was found to have comparableviscosity at higher shear rates.

FIG. 44 shows a comparison between the rheology of 12 ppg Sodium bromidebrine viscosified with 3% STABILEZE QM at a pH of 7, 8 and 10 at 75° F.,107° F. and 140° F.

CONCLUSION

The STABILEZE QM can be used to gel 10.8 ppg formate, 15.6 ppgcesium/potassium formate and 18.5 ppg cesium formate by adding theSTABILEZE QM to the formates. The STABILEZE QM can be also be used toviscosify 12 ppg sodium bromide brine by adding STABILEZE QM to thebrine and neutralizing to a pH ranging from about 7 to about 10 with 50%sodium hydroxide. As the sodium hydroxide is added, the fluid will gel.

Results of testing in 10.8 ppg sodium/potassium formate indicate thatwhen completely mixed, the 2% STABILEZE QM in 10.8 ppg Na/K formate hascomparable viscosity at 75° F. and at 107° F. The fluids haveapproximately 100-110 cP at 100 sec-1. The STABILEZE QM continues tosolubilize with time and temperature.

Results indicate that when completely mixed, the 2% STABILEZE QM in 15.6ppg cesium/potassium brine has comparable viscosity at 75° F. and at107° F. The STABILEZE QM continues to solubilize with time andtemperature. The viscosity of the 2% STABILEZE QM in 18.5 ppg Cs formateincreases with temperature. The viscosity of the 2% STABILEZE QM in 18.5ppg Cs formate at 75° F., 107° F., 140° F. and 180° F. is 89, 98, 183,and 387 cP at 100 sec-1, respectively. The viscosity of the 2% STABILEZEQM in 18.5 ppg in Cs formate brine at 75° F., 107° F., 140° F. and 180°F. is 309, 250, greater than 875, and 5605 cP at 1.7 sec-1,respectively.

Rheology results of 12 ppg Sodium bromide viscosified with 3% STABILEZEat pH 7 indicate a viscosity of the fluid at 75° F., 107° F. and 140° F.is respectively 627, 409, and 471 cP at 100 sec-1. The viscosity of 12ppg sodium bromide with 3% STABILEZE QM buffered to a of pH 8 at 75° F.,107° F. and 140° F. is 495, 380, and 325 cP, respectively, at about 100sec-1. Viscosity of 3% STABILEZE QM in 12 ppg Sodium Bromide buffered toa pH of 10 at 75° F., 107° F. and 140° F. is 555, 365, and 287 cP,respectively, at about 100 sec-1. At 140° F., 12 ppg sodium bromideviscosified with 3% STABILEZE QM delivered the maximum viscosity whenthe fluid was buffered to a pH of 7 at 100 sec-1. 12 ppg Sodium bromideviscosified with 3% STABILEZE buffered to a pH of 7 was developed to amaximum viscosity at higher shear rates when it was buffered to 7 pH.

At all different buffer conditions the STABILEZE QM continued tosolubilize with temperature and time.

What is claimed is:
 1. A well servicing fluid formulated withingredients comprising: a viscosifying polymer that is a crosslinkedcopolymer of an ethylenically unsaturated dicarboxylic anhydride and analkyl vinyl ether, or the di-acid thereof; a pH adjuster that maintainsa pH of greater than 5.5; a non-emulsifier; and a solvent containing asolution of alcohol and aqueous base, the solvent ranging from about 75%to less than 95% by weight based on the total weight of the wellservicing fluid, a concentration of the viscosifying polymer in the wellservicing fluid being at least 15 pounds per thousand gallons (pptg) andthe viscosifying polymer exhibiting structural and chemical propertiessufficient to yield a viscosity of at least 23 cP at 102 sec⁻¹ for thewell servicing fluid at the concentration.
 2. The fluid of claim 1,wherein the ether has the formula ROR′, where R is a C₁-C₄ alkyl and R′is a vinyl group.
 3. The fluid of claim 2, wherein the ethylenicallyunsaturated dicarboxylic anhydride is maleic anhydride.
 4. The fluid ofclaim 3, wherein the ether is methyl vinyl ether.
 5. The fluid of claim1, wherein the crosslinked copolymer is crosslinked using an alpha,omega diene having from 6 to 20 carbon atoms.
 6. The fluid of claim 1,wherein the viscosifying polymer is a poly (methyl vinyl ether/maleicanhydride) decadiene crosspolymer.
 7. The fluid of claim 1, wherein thedi-acid is a poly (methyl vinyl ether/maleic acid) decadienecrosspolymer.
 8. The fluid of claim 1, wherein the solvent comprises atleast one alcohol chosen from methanol, ethanol, propanol and butanol.9. The fluid of claim 8, wherein the solvent comprises at least 20% byweight alcohol, based on the total weight of the solvent.
 10. The fluidof claim 1, further comprising nitrogen gas, liquid carbon dioxide orsupercritical carbon dioxide.
 11. The fluid of claim 1, wherein thesolvent comprises brine having a salt concentration of 0.5% by weight orgreater.
 12. The fluid of claim 11, wherein the brine comprises at leastone salt chosen from halide salts and formate salts.
 13. The fluid ofclaim 11, wherein the brine comprises at least one salt chosen fromNaCl, KCl, CaCl₂, MgCl₂, NH₄Cl, CaBr₂, NaBr₂, ZnBr₂, sodium formate,potassium formate, and cesium formate.
 14. The fluid of claim 1, whereinthe pH adjuster is chosen from NaOH, KOH, Ca(OH)₂, sodium bicarbonate,potassium carbonate, and sodium carbonate.
 15. The fluid of claim 1,further comprising a breaker.
 16. The fluid of claim 15, wherein thebreaker is a compound chosen from percarbonates, perchlorates, peracids,peroxides, persulfates and encapsulated potassium persulfates.
 17. Thefluid of claim 1, wherein a proppant is mixed with the well servicingfluid.
 18. The fluid of claim 1, wherein the solvent is chosen fromfresh water, brine, and produced water.
 19. The fluid of claim 18,wherein the solvent is seawater.
 20. The fluid of claim 1, wherein thefluid is formulated with at least one additional compound chosen fromadditional viscosifying agents, surfactants, clay stabilizationadditives, scale dissolvers, biopolymer degradation additives, fluidloss control additives and high temperature stabilizers.
 21. The fluidof claim 1, wherein the well servicing fluid is in the form of a gel andthe gel contains the non-emulsifier.
 22. The fluid of claim 21, whereinthe well servicing fluid is in a well in a formation.
 23. The fluid ofclaim 1, wherein the solvent comprises at least 75% by weight alcohol,based on the total weight of the solvent.
 24. The fluid of claim 23,wherein the viscosifying polymer concentration is 15 to 60 pptg and thesolvent comprises 75% to 95% by weight alcohol, based on the totalweight of the solvent.